1. Field of Invention
The present invention relates in general to the field of microfluidics. More particularly, the present invention relates to using thermally cross-linkable photo-hydrolyzable inkjet printable polymers and inkjet printing to fabricate one or more microfluidic channels layer-by-layer in a substrate body.
2. Background Art
The field of microfluidics emerged in the 1980s and has enabled the development of many microscale technologies, including DNA chips, lab-on-a-chip devices, and precision inkjet printing. Microfluidics provides the ability to deliver nanoliter and picoliter volumes of liquids by direct application, such as inkjet printing, or via continuous flow through microfluidic channels. Unfortunately, the current process for the creation of three-dimensional microfluidic channels, i.e., the 2-photon writing process, is expensive and extremely complex.
The current 2-photon writing process involves the application of an acid-hydrolyzable polymer brush, poly(tetrahydropyranyl methacrylate) (PTHPMA), onto a glass surface. Interstitial spaces are filled in via spin coating with a mixture of a photoacid generator (PAG), a sensitizer, and a copolymer of methyl methacrylate and poly(ethylene glycol) methylether methacrylate. Once the mixture has been spin coated onto the glass surface, a pulsed laser source (e.g., a Ti-sapphire femtosecond laser) is used to effectively carve out a channel of acid in the PTHPMA. The pulsed laser source is precisely focused and rastered through the PTHPMA in a pattern that defines the channel. This results in localized 2-photon generation of acid (i.e., the PAG is exposed within localized regions of the PTHPMA and releases acid only within those regions) in the PTHPMA. A 2-photon writing process is required to maintain the necessary spatial resolution (otherwise, the PAG would be exposed throughout the entire thickness of the PTHPMA and release acid everywhere). The photoacid hydrolyzes the PTHPMA during heating, forming hydrophilic poly(methacrylic acid) (PMAA) in the form of a three-dimensional hydrophilic channel traveling through a hydrophobic substrate. The 2-photon writing process requires precise calibration and alignment of one or more femtosecond lasers, which is costly and difficult to execute. An example of a 2-photon writing process is disclosed in Lee et al., “Multiphoton Writing of Three-Dimensional Fluidic Channels within a Porous Matrix”, Journal of the American Chemical Society, Vol. 131, No. 32, 2009, pages 11294-11295, published on Web Jul. 28, 2009, which is hereby incorporated herein by reference in its entirety.
Therefore, a need exists for an enhanced mechanism for fabricating one or more microfluidic channels in a substrate body.